A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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Choosing between Chi-Square/Logistic Regression Vs Difference of Mean tests for predicting bankruptices

You'd expect more companies to go bankrupt if they have low cash balances. Of course, bankruptcies can also happen even when you have lot of cash on hand (to terminate labor contracts, etc.). The ...
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1answer
23 views

impact on hypothesis if t-stat is equal to t-critical value for one-tail two-sample t-test? [duplicate]

I have a two-sample t-test where the t-statistic is equal to the critical t-value (at three decimal points) at a p-value of 0.05. does this mean i reject the null hypothesis or the opposite? thank you ...
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1answer
48 views

Mann-Whitney test

I am carrying out a study in which I have $3$ groups $n= 2$, $n= 5$, $n=17$. Each group has a different inner ear abnormality, following the fitting of an ear implant I have measured their speech ...
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5answers
76 views

Unequal variances t-test or U Mann-Whitney test?

I have two independent samples and I need to compare their values, to say if values in the first group are higher than values in the second group. I performed the Levene's test and the variances are ...
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2answers
24 views

When doing a t-test for the significance of a regression coefficient, why is the degrees of freedom n - predictors - 1?

I read at http://www.unesco.org/webworld/idams/advguide/Chapt5_2.htm that this was the degrees of freedom I should use, but I don't understand why. My understanding was that t-tests generally had n-1 ...
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1answer
26 views

T test assumptions

I'm performing a t-test on a time series with a sliding window (i.e. every N samples, perform a t test). I know that overall, the samples are roughly normally distributed, however adjacent samples ...
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1answer
73 views

How to get P-Value when t value is less than 1?

I am doing an assignment for class and I have hit a wall. I'm not sure what to do next. Using a sample with 12 discrete elements, I am trying to test a hypothesis that the population mean is 243 ...
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1answer
34 views

t-test what needs to be normally distributed? [duplicate]

I'm aware that the t-test needs 'normally distributed data'. But take the variable y. When it is plotted without being split by ...
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148 views
+150

What could be a statistical test for comparing funnel data before and after important changes?

I have some funnel data from a website I manage. After some time I did some improvement on a multi-step purchase process. I wonder if it's possible to formulate a test that with statistical ...
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1answer
18 views

Bootstrapped t test in SPSS: Why are some p value cells blank?

Using an independent samples t test, I am comparing the performance of 2 groups on an activity, based on the percentage of items correct (the percentage of total items correct, as well as percentage ...
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21 views

Can I use a paired-samples t-test when the 2 groups that I compare have different numbers of data points?

I want to compare the effect of a drug (immunomodulator) on antibody levels in a group of patients $(n=18)$. Blood samples were taken pre- and post-treatment in each patient and the means of antibody ...
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1answer
29 views

Bootstrapping t-test for nonparametric data

I have a two heavily skewed distributions and am trying to use bootstrapping to compare their means via the t-test. I am concerned about the appropriateness of using the standard error of the ...
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1answer
92 views

Why is the Tukey confidence interval wider than the T-test confidence interval?

I have two confidence intervals for a comparison of two means. The first is a t-test CI and the other is a Tukey CI. The Tukey CI $(2.36, 26.5)$ is wider than the t-test CI $(6.46, 21.33)$. What is ...
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1answer
18 views

Reporting bootstrapped output for an independent samples t test

When reporting results of a bootstrapped independent samples t-test, can I just report the t statistic alongside the bootstrapped p value? Or do I also need to report confidence intervals?
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2answers
27 views

T test with one group

I think it is a simple question, but I got many different results and now I am not sure which test to use. I have one group and 2 different scores (higher scores means higher either positive or ...
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2answers
45 views

How much is moderate violation to normality for one sample t-test?

I want to test if my data have a mean equal to zero (Ho: mu=0). The sample size in not large (n=21). My variable is numerical with average -0.10 and sample_sd 0.05. I don't know the population ...
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1answer
24 views

Non parametric one sample t-test alternative with a binary variable

I am doing an analysis of items (I1, I2, I3, etc.). The items could be either correctly answered (1) or incorrectly answered (0). Visually, most of the participants answered the items correctly. I ...
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21 views

Is pairwise wilcoxon test a valid non-parametric alternative to Tukey's HSD test?

I am trying to identify significant differences between groups from normal and non-normal distributions. When the distribution is normal the workflow is pretty straightforward: ANOVA and after that a ...
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1answer
40 views

Can i do a paired t-test on a pre- and post questionnaire but without pairing the same student for the pre and post?

I really suck at this so hope you could help me ve a group of people attending a training course, in order to measure whether the training course is effective in improving attendees' knowledge. We ...
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0answers
35 views

Overlapping sample t-test

I have 10 people working together. They work in group for 6 days. Three days in week 1, three days in week 2. In each day I don't have the full set of people, but a subset of them. In each day I ...
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1answer
94 views

Does one lose information or precision when calculating effect sizes from statistical values rather than from the raw data?

Let's say that I want to compute the effect size of a certain intervention, for which I have both the raw data and some statistical value that can be transformed to an effect size. For example, if one ...
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2answers
36 views

Paired t-test of medians

I need to run an inferential test on some large data where the individual data points have a heavily skewed distribution. I'm considering doing a paired t-test across a number of days comparing the ...
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25 views

Confused about how to work through this t-test problem

So, I'm working on this homework problem and am really unsure how to go about it. I'm working with an online software, which gives me the answers to the questions, but I have no idea how to get to ...
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2answers
82 views

Why use a z test rather than a t test with proportional data?

When testing the difference between 2 proportions why do we use a z-test rather than a t-test? Further, is there a simple way to conduct an omnibus test for significant differences between more ...
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1answer
36 views

example where comparison of three mean anova and t-test have different results

suppose to have sample from 3 groups A,B,C. The hypothesis H0: the mean of the 3 groups is the same can be tested using 3 independent t test. ...
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1answer
20 views

Which test is useful to assess if a source is the same in two samples of binary data?

I am looking for a statistical test that assesses if two samples which have binary values come from the same source or from different ones. Example: I have one set that has 10 0s and 6 1s and ...
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1answer
35 views

Picking the right statistical test

Definite stats newbie, and I'm looking for a little bit of direction on which statistical test to use. Here's a quick summary: I'm trying to determine if the cases are on more than one narcotic at ...
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0answers
28 views

Minimum sample size for t-test [duplicate]

Can you do a t-test or ANOVA between 2 or 3 groups respectively if one of those groups has a sample size of 2? Are the results interpretable in the same way as with larger sample sizes(n=4,5,6?). If ...
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29 views

Bootstrap approach for testing differences in interquartile range suitable?

I am investigating differences in two groups of forecast errors (absolute values / unsigned) that both have a strongly right-skewed distributions. Both groups of errors have the same number of ...
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1answer
45 views

Comparing two means: Same group, different variance (Welch's t-test?)

Intro: I have recently made a simulation program which simulates patients with Type 1 diabetes. In that context I am creating artifical patients. Let's denote three of these as $\text{p}_1$, ...
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0answers
33 views

What statistical tests can be used on a distribution of distributions?

I have two experimental conditions, each with 20 reps (40 experiments total). In all 40 experiments a non-fixed number of sounds were recorded, and I've measured each of their durations. I would now ...
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21 views

Confused about t-contrasts, F-contrasts and the associated tests (t-test, ANOVA)

What is the difference between a t-test and a contrast tested using a t-test? When would an F-contrast be used instead of a regular t-contrast? Is the relationship between the two the same as between ...
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1answer
20 views

(Inverse) proportionality between significance and effect size, for a fixed sample size?

This is a question to hopefully untangle the sometimes confounded notions of statistical significance and effect size. As far as I understand, sample size intermediates the relationship between them, ...
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13 views

t-test correction for serial correlation

I have a time series of serially correlated data (differences between spatial means of meteorological variables). I calculated the lag-1 autocorrelation (rho), and corrected the number of degrees of ...
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14 views

Dichotomised data-how to test for a difference(potentially independent t-test) SPSS

I am using a 2X3X4 design, which has the following ivs: Social Anxiety Scores(formed two groups,essentially high and low scores) 3 emotions and 4 gaze directions. I need to test if the groups are ...
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1answer
44 views

Is it ok to compute statistics on t-values?

Background I have a population in which my dependent variable is binary with a highly-skewed distribution: Very few records are 1 (doers), most records are 0 (non-doers). I'm using logistic ...
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1answer
28 views

(very basic) One-sample test for binary data

I've repeatedly measured a continuous variable and each measure has been assigned a populational percentile range it falls into (percentile ranges were estimated for general population in another ...
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0answers
26 views

Composite Scores and Standardized Composite Scores t test

I have a set of survey data related to 20 survey questions. Each of these questions represent a variable (Q1, Q2,......
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0answers
23 views

Statistical testing: Multiple classifiers, 1 domain. Would rANOVA be appropriate?

When comparing the performance of two classifiers over a single domain, in the context of a classification problem in machine learning, it is common to use a paired t-test, using the 10 average ...
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0answers
43 views

How to perform hypothesis testing for comparing different classifiers

I am trying to classify a small dataset (around 500 records) into two classes. I used various methods like SVM, Naive Bayes and k-nn classifier. Now, I would like to set the results from one of the ...
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1answer
32 views

Is variance replacing square of standard deviation in a t test?

I am writing a t test using the code here : How to perform two-sample t-tests in R by inputting sample statistics rather than the raw data? But I would like to use the root of the variance as an ...
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0answers
15 views

How to summarize mean +/- S.D. across disease severity

I am performing a meta-analysis and I have several papers that measure compound X in the blood of patients with a given disease. These papers have classified patients into groups based on disease ...
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1answer
55 views

Which statistical analysis replaces MANOVA when there are too many dependent variables?

I want to understand if an experiment gives equal response at two different levels of an experimental parameter. What I did was to repeat the experiment 6 times at the first level of the parameter and ...
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1answer
102 views

Which test should be used to compare two mean differences?

Say that I have two groups who received two treatments, and now I want to know if they progressed AND which group progressed more. I first did a paired t-test to know their progress, respectively, and ...
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1answer
35 views

Total scores are normally distributed, but subtest scores are not; what to do?

I have two sets of data for males and females: $n=33$. I'd like to compare test results for both groups. I want to do a $t$ test, and I know my data should be normally distributed if I want to use a ...
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0answers
17 views

Paired t-test and random intercept model

It's known that the paired t-test is equivalent to the random intercept model in the sense that the data for paired t-test is actually two repeated measures on the same subject and we can use a ...
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4answers
527 views

How can a t-test be statistically significant if the mean difference is almost 0?

I am trying to compare data from 2 populations to tell if the difference between the treatments is statistically significant. The data sets appear to be normally distributed with very little ...
3
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2answers
211 views

Calculating statistical significance with unequal sample sizes and unequal variances

I have two samples, one with $n_1 = 41,000$ and the other with $n_2 = 881$; the larger sample has a standard deviation of $13.74$, and the smaller has an $SD=10.75$. The means are different, and when ...
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0answers
13 views

Test whether distribution of random values converges to fixed value

I conduct a simulation experiment which produces values with some random effects involved. In theory, the results should all be some fixed value $c$. What is an appropriate test to check whether the ...
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0answers
99 views

Demonstrate difference in growth over time

Short version Is there a difference per treatment given time and this dataset? Or if the difference we're trying to demonstrate is important, what's the best method we have for teasing this out? ...